It is a hard slog running a major European investment bank these days. New rules from the US Federal Reserve won't help much. But they could have been a lot worse.

The Fed is trying to increase its oversight of large foreign banks including Deutsche Bank and Barclays so that their US units don't fall short on capital or liquidity. That means, for example, that foreign banks with large US operations will have to hold qualifying equity equivalent to 3% of their assets.

On the face of it, banks that have run capital-light models could have to raise new funds. But they will have until 2018 to meet the rules, rather than until mid-2015 as previously feared. Banks could make up capital shortfalls by accumulating retained earnings or shrinking their balance sheets steadily.

Other potential headaches look manageable. One worry was that the Fed might force foreign banks to rely more on funding themselves within the US, rather than relying on cheap loans from their parents. But the final rules suggest such parent-to-subsidiary funding won't be penalised, according to analysts at JP Morgan.

Sure, foreign banks will have to set up local holding companies with their own risk committees and a chief risk officer. Another bureaucratic issue, yes. But a game-changing imposition, no.

Still, all this may prove only temporary relief. US banks have in general made more progress in repairing their balance sheets and adjusting their business models than their European peers. Banks such as Deutsche and Barclays are still in the middle of substantial deleveraging programs, while weighing which business lines they can and can't afford to be in.

That is having an impact. Both Barclays and Deutsche lost market share in the all-important fixed income, currencies and commodities business last year. Rivals JP Morgan, Goldman Sachs and Citigroup all gained, based on data from brokerage Jefferies.

And while the Fed's rules may not be as problematic as feared, they still add to growing worries about the Balkanisation of global banking. Already, European politicians have objected to the Fed imposing tougher rules on European banks than US banks face in Europe. That raises the prospect of regulatory tit for tat.